oldest messages are still in mailbox store

Hello!

Planning the migration OSE6.x from U8.04/32 to U10.04/64.
Experimenting with different backup methods. Found this nice script. Changed it a bit (see attachment): corrected found mistakes etc. Meld it against original one.

But on analysis of the backed up data I discovered that mailboxes' STORE directories stores tons of old messages, which were removed and purged long time ago. For example, default CoS stores messages in mailbox for 30 days, spam and trashcan for 15 days (*). And I was surprised seeing on January 25, 2012 the stored messages of year 2009. They aren't in any of mailbox's directories. And counter may show "used 0 of 150 megabytes", because no any single message is in any mailbox's directory at all.

But these messages occupies a storage space. How to get rid of these in "orthodox way"?